<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

</body>

</html>
<script>
    // 给你一个字符串 s ，将该字符串中的大写字母转换成相同的小写字母，返回新的字符串。
    function toLowerCase(str) {
        let ret = ''
        for (let i = 0; i < str.length; i++) {
            let code = str.charCodeAt(i)
            if (code <= 90 && code >= 65) {
                ret += String.fromCharCode(code + 32)
            } else {
                ret += str[i]
            }
        }
        return ret
    };
    console.log(toLowerCase("strSTR"));

</script>